2. Field of the Invention
The present invention generally relates to a magnetic levitation system and, more particularly, is concerned with a magnetic levitation system for the stable levitation of a body.
2. Description of the Prior Art
An electromotive force is produced in a conductor when there is a change in magnetic flux through a conductor. Thus relative motion between a conductor and a magnetic field will cause a conductor to cut the flux of the magnetic field producing an induced electromotive force across the conductor. Currents set-up in a substance by variation of an applied magnetic field are called eddy currents. Energy is dissipated by eddy currents usually in the form of heat. Eddy currents in a moving conductor also react with the magnetic field to produce retardation of the motion and thus have a damping effect on the motion. The induced currents produce a magnetic field above the conductor which opposes the original magnetic field.
Magnetic levitation of an object has been achieved in various forms in the past. This technology is currently being developed for application in magnetically levitated trains.
U.S. Pat. No. 3,327,265 to Geuns et al describes a magnet which is levitated above a superconducting material where two apertures are cut in the superconducting material to cause the magnet to align in a certain direction.
U.S. Pat. No. 3,589,300 to Wipf discloses a magnetic suspension system where a propelled magnet is levitated by repulsion from eddy currents that are induced in a continuous conductor. In this invention the axis through the poles of the magnet extends in the same direction as the continuous conductor. Stabilization of the levitation is achieved by constructing the conductor with short bars or legs to produce restoring forces created by the eddy currents induced in the short bars or legs.
U.S. Pat. No. 3,892,185 to Guderjahn discloses an improved magnetic suspension system where the guideway is formed from a combination of non-ferromagnetic material and ferromagnetic material. The guideway is formed in the shape of a channel having top, bottom and side portions to provide a more rigid suspension and one more resistant to oscillations. Any displacement of the magnet from the middle of the channel will result in restoring forces which tend to move the magnet back to an equilibrium position.
U.S Pat. No. 4,797,386 to Gyorgy et al discloses the use of superconducting elements to induce lateral stabilization in a magnet created either by a permanent magnet or a magnetic field created by a flowing current. Gyorgy et al state that through the use of a superconducting material, lateral stabilization can be achieved above a superconducting element which is planar, or an inverted cup shape.
All of the above prior practices address the topic of rigid or stable levitation which is the attempt to maintain the levitated body in an equilibrium position. The inventions of Wipf and Guderjahn require that the guideway be designed with a more complex geometric configuration, such as a surface with more than one side to achieve lateral stable levitation. Geuns et al and Gyorgy et al require superconducting materials to achieve stable levitation. None of the prior practices recognize the importance of the orientation of the magnet with respect to the direction of relative motion between the magnet and the conductor in achieving rigid levitation.
A need therefore exists for a magnetic levitation system which achieves rigid levitation above a flat guideway without the use of superconducting materials or sidewalls for stabilization. Such a guideway could be constructed at a much lower cost and would be useful in applications such as magnetic levitation of trains and studies of aerodynamic flow around bodies.